This invention relates to gaseous discharge panels and more particularly to an improved method of constructing a gaseous discharge display/storage device which provides significant improvements in both the static and dynamic margins of the device while increasing the stability of the operating voltage of the device.
In the fabrication of gas panel assemblies, parallel metal electrodes are deposited onto the surface of a glass plate or substrate and a layer of insulating glass dielectric frit or slurry applied over the surface of the conductors to provide a smooth film of substantially uniform thickness across the entire surface. When the glass plates have been cooled, an overcoat layer of a refractory secondary emissive materials such as MgO (magnesium oxide) is evaporated over the dielectric layer by inserting the panel into a vacuum chamber for the evaporation. The refractory aspect prevents sputtering of the dielectric by ion bombardment, while the high secondary emission permits lower operating voltages. The plates are then edge sealed to form a chamber which is controlled to provide a uniform gap across the entire display area of the panel. Conventionally, the panel is then baked in vacuum to eliminate impurities and residual gasses including water vapor from the surface of the dielectric. Such a bakeout cycle is a time consuming operation in that approximately 16 hours is required to raise the panel to the desired temperature, maintain it at this temperature for 5 hours and then reduce the temperature from an elevated to room temperature such that a substantial length of time is involved in this aspect of fabrication. After baking, the panel is backfilled with a gas capable of emitting light in response to an electric voltage applied simultaneously to the orthogonally disposed conductors. When the panel fabrication has been completed, the electrical parameters are stabilized by a burn-in cycle in which all cells in the panel are turned on for a period of 7 hours at a specified voltage and frequency. The static operating margin of the panel, i.e., the difference between the maximum sustain voltage (V.sub.s max.) and minimum sustain voltage (V.sub.s min.) required to sustain the lines in the panel is then tested. During normal panel operation, or under test, the maximum and minimum sustain voltages defining the static margin of the panel tend to converge, effectively destroying the operating margin and reducing the yield of the panels thus fabricated thereby significantly raising the cost.